All that Glitters...

Examination of the chemical abundances in the solar system leads me to suspect that, no, future people will still use gold much the way we do now.

And I've been thinking about how you'd launder whatever precious metal you were using as a de-facto commodity money—you're using it to avoid the paper-trail (which I guess a paperless setting calls an audit trail?) inherent to purely electronic currency, so you need a way to turn it into money you can use. (In a society like that, insisting on doing business in gold means you're shady, automatically.)

One thing I thought of would be, asteroid miners. Space-travel is relatively cheap in my setting—for non-fragile payloads that don't need life-support and can survive the 30 g-force acceleration of something like a Generation 1 StarTram mag-lev space launch, it's $43 a kilogram, which is comparable to shipping a package by mail. You ship it to a confederate, perhaps first re-combining the gold with other minerals (so it looks like ore), and then he takes it to some ore-processor, and you get money back. The only trouble there is there's at least two middlemen, the confederate and the ore-processor.

Ah, got it. Modified version. You sell the gold, as-is, and semi-above the table, to someone at your local COPUOS office. Presumably you have a shell-corporation/cover-identity as a mineral speculator, i.e. a person who buys and processes the produce of asteroid miners.

(An "asteroid miner" in my setting, come to think of it, is not really a person who ever sets foot anywhere near an asteroid—they're a person who owns and remotely operates asteroid-mining robots. So maybe your cover is just "asteroid miner", rather than the middleman. "He's registered as an asteroid miner but never actually leaves the planet" isn't a problem, although "no craft registered to his name has logged any deposits down whatever chute gets the minerals planetside from space" might still be. And yes, you put your mining-produce down a chute, you don't want to just drop it on the planet, first because safety and second because "claim-jumping". Maybe a criminal money launderer just owns some asteroid drones that periodically shove whatever dirt they collect down the chute, so as to keep up appearances.)